Banjo resonator



Feb. '26, 1924. 1.485,l55

A. M. ANDERSON BANJO RESONATOR Filed Iggy 1.922

Patented Feb. 26, 1924.

UNITED STATES ALBERT M. ANDERSON, OF SEATTLE, WASHINGTON.

BAN J O RESONATOR.

Application filed May 22, 1922. Serial No. 562,782.

7 '0 all whom it may concern:

Be it known that I, ALBERT M. ANDER- SON, a citizen of the United Statesof America, and resident of the city of Seattle, in the county of Kingand State of VVashington, have invented certain new and usefulImprovements in Banjo Resonators, of which the following is aspecification.

My invention relates to an. attachment in the form of a resonator forbanjos, mandolin-banjos, and like musical instruments which have astretched head and a rim which is open at its under side.

The object of my invention is to provide a resonator which willconsiderably increase the volume of sound produced from the instrumentwith like playing effort, and to mellow and soften the tone thereof.

In accomplishing this object I provide means whereby the original soundwaves are divided and led off, and thus are not reflected back towardsthe vibrating head to interfere with other subsequent sound waves.

My invention is embodied in the novel attachment or resonator which isshown in its present preferred form in the accompanying drawings. I

Figure 1 is a transverse section taken on the central line of the banjoand resonator.

Figure 2 is a plan view of a banjo with the resonator attached.

Figure 3 is a detail section showing the means of attaching theresonator to the banjo.

The banjo comprises the rim 11, the stretched. head 1, and strings 12supported by a bridge 13 and extending to the outer end of a stem 14. Tothis banjo I attach a resonator in some suitable manner, the attachingmeans being unimportant. The resonator comprises a bowl-like shelldesignated generally by the numeral 2. The attaching means which I haveshown comprise a plurality of brackets 20 which are secured to theresonator and which frictionally engage the outer periphery of the banjorim 11. It will be apparent that any other suitable securing means maybe employed.

The shell 2 lies beneath the open side of the banjo. At about the centerof the head 1 it rises to a conoidal peak 21. The peak 21 is preferablybeneath the playing center or center of vibration of the banjo head.This may or may not be atexactly the cen ter of the circular head 1, butwill be sub stantially at this .point, and therefore for most playersand most instruments centrally positioned peak 21 is preferable. Fromthe peak 21 the resonator extends downwardly in all radial. directionsin a smooth curve. Preferably it is provided with a rim 22. The surface223 between the rim 22 and the peak 21 is formed as a curve which mergesinto both the rim and the peak. The rim is notched as indicated at 24-to receive the heel of stem 14. Preferably this heel does not touch theedges of the notch 24.

The sound waves inwardly projected from the banjo head strike theresonator or deflector and by reason of its curved shape are deflectedoutwardly in all directions from the peak 21 and forwardly through theannular opening between the resonator rim 2 and the banjo rim 11, thusadding to and reinforcing the sound waves which are originally projectedoutwardly. Vibrations are also induced in the resonator in harmony withthose given off by the banjo. It acts both as a deflector and as anamplifier of the sound.

It is essential that the peak be provided in the resonator because ifthis is omitted the sound waves will merely be reflected back and forthbetween the resonator and the head 1 and interference will result. Byproviding an open sound conduit extending from the central peak in alldirections about the rim 11 of the banjo, and curved to prevent directreflection, the sound waves are led outward and do not interfere withadditional waves originating in the head 1. This is the essence of myinvention and while the general curve of the resonator may be varied andwhile the rim 22 might be omitted, it is essential that the peak 21 beprovided and that it be positioned substantially beneath the center ofgreatest vibration of the head 1. I

What I claim as my invention is:

1. A resonator for banjos comprising a shell adapted to cover the openback of the banjo, and means for attaching the shell to a banjo, thesurface of said shell which faces the banjo head sloping from a sharpcentral point towards its periphery in all directions by a curve of aradius at least substantially equal to the radius of the banjo.

2. A resonator as in claim 1, the attaching means comprisingfrictionally engaging inturned lugs spaced about the periphery of theshell.

3. A resonator for banjos comprising a bowl-like shell adapted to coverthe open back of the banjo, and of greater diameter than the banjo, saidshell including a rim formed about its periphery and extending about therim of the banjo, and directed for wardly, the surface of said shellwhich faces the banjo head sloping from a sharp central point in alldirections to merge with the rim by a curve of a radius at leastsubstantially equal to the radius of the banjo, and means for attachingthe shell to a banjo.

i. A resonator as in claim 3, said attaching means comprising membersspaced about and secured to the inner surface of the rim only, andengageable with the banjo rim.

5. In combination with a banjo or like musical instrument, a resonatorcomprising a bowl-like shell of slightly larger diameter than the banjohead, and including a peripheral rim extending about and spaced from thebanjo rim, and a sharp substantially centrally positioned peak upon theinner surface of the shell, said shell forming with the banjo a soundchamber curving from said peak downward and outward in all radialdirections by a curve of radius at least substantially equal to theradius of the banjo, and then upwardly outside of the banjo rim.

6. A resonator for banjos and like musical instruments comprising ab0wl-like shell having a marginal rim and a sharp central peak, thesurface between the rim and peak being formed on a curve which isconcave in cross section towards the banjo at all points, and whichmerges into both peak and rim.

7. A resonator for banjos and like musical instruments comprising asubstantially circular shell having a sharp central peak, the surfacebetween the periphery and peak being formed on a curve which is concavein cross section tow: rds the banjo at all points, and the center ofcurvature of which follows a circle lying towards the periphery of theresonator from an axis extending through its center.

Signed at Seattle, Kinp County, ashiugton, this 16th day of l\ ay 1922.

ALBERT M. ANDERSON

